Warning on Soft Contact Lenses : Cleaning With a Sterile Saline Solution Now Urged
Soon after soft contact lenses were introduced, wearers began to complain that the preservative-treated solutions they bought off store shelves to rinse and store the contacts irritated their eyes.
To solve that problem, ophthalmologists and optometrists told sensitive people to mix their own solutions at home, using salt tablets dissolved in distilled water.
Now it appears that advice has caused a larger problem for some people--one largely to blame for an outbreak among lens wearers of a new and often blinding eye infection called acanthamoeba keratitis.
The American Academy of Ophthalmologists and the Contact Lens Assn. of Ophthalmologists now say soft-lens wearers should treat their lenses only with commercially prepared, sterile, saline solutions.
Twice during the past two months, the two organizations have issued warnings urging the country’s 23 million contact-lens wearers to change their lens-cleaning habits--or risk contracting the infection.
A Painful Condition
The first symptoms of acanthamoeba keratitis are redness and tearing of the eye. Most sufferers initially are misdiagnosed as having minor bacterial infections. But as the condition progresses, the condition becomes severely painful and causes a progressive loss of vision.
“It’s a very disabling disease,” said Dr. Mark Mannis, an eye expert at UC Davis. Mannis has treated two Northern California patients with the ailment.
As an alternative to mixing their own home solutions, contact-lens wearers who are allergic to preserved solutions can buy commercial products that do not contain preservatives. But, the groups stress, these preservative-free solutions must be refrigerated and discarded after a week. Distilled water is not sterile and shouldn’t be used.
Although only two cases of acanthamoeba keratitis have been reported among hard-lens wearers, Dr. Perry Binder of San Diego recommends that they, too, rinse and store their lenses only in commercially prepared, and preferably preserved, sterile, saline solutions. Binder is president of the contact-lens association. Until now, eye doctors, optometrists and opticians have told hard-lens users to rinse their contacts with tap water after cleaning them.
Unfamiliar to Most Doctors
Acanthamoeba is a common protozoan that inhabits water and soil. Scientists have cultured it from hot tubs, sewers and the human throat, among other sites. However, the organism is unfamiliar to most doctors. In fact, until 1973, when Dr. Dan Jones at Houston’s Baylor College of Medicine diagnosed acanthamoeba in a rancher’s eye, the organism was thought to cause only one illness in man--an extremely rare but fatal form of meningitis.
Only 31 cases of acanthamoeba keratitis, the eye condition, were documented in the United States between 1973, when the ailment was first identified, and 1985. But in the past 12 months alone, the Centers for Disease Control in Atlanta has gathered reports of 46 of the infections.
The CDC has been able to clearly document 24 cases of those diseases. Out of those, all but four sufferers wore contact lenses, according to Govinda Visvesvara, a CDC researcher. And of the lens-wearers, only two wore hard contacts. The others used soft lenses--primarily the daily-wear variety. Lens-care information was unavailable for four of the patients.
Of the remaining 20, 15 rinsed their lenses either with homemade solutions, tap or well water. Visvesvara cultured lens cases belonging to three of the patients who used homemade solutions, and found that all three contained acanthamoeba. However, Visvesvara declined to take a position on specific causes of the problem.
No Homemade Solutions
“There is a danger and people have really got to stay away from homemade solutions and tap water,” said Binder, who also urges wearers to remove lenses during gardening and swimming and in other situations where their eyes might be splashed with water or contaminated with soil.
Doctors generally have been slow to diagnose acanthamoebae. In published cases of the ailment to date, it took people with infected eyes from seven weeks to 12 months to get the correct diagnosis. In three instances, the organism was not identified until after the patients’ eyeballs were surgically removed.
Investigators, including Visvesvara and Jones, attribute the current outbreak to today’s larger number of lens wearers, the use of homemade solutions, and doctors’ improved skill at recognizing the ailment.
Ophthalmologists hope earlier identification and treatment will improve the prognosis for people with the disease. To date, only five cures with drugs alone have been reported in the medical literature. The other patients have required one or more surgeries to cut out the organism.
Reports from Great Britain hold hope that an agent in widespread use there, propamidine isethionate, may offer a cure. But the drug, sold under the trade name Brolene, is available only on an experimental basis in the United States, said a spokeswoman for the U.S. Food and Drug Administration.
A Hardy Organism
Ophthalmologists believe most of the infections reported so far could have been prevented if patients merely had used sterile solutions. But for a few patients, that would not have made a difference.
Acanthamoebae are unusually hardy organisms. When they encounter adverse conditions, they form into double-walled cysts that can withstand drying and freezing, as well as most drugs in an ophthalmologist’s pharmaceutical arsenal. For most patients, corneal transplant has been the only successful treatment. Even after surgery, though, few recover full vision.
Eye doctors say long-term contact-lens wear causes microscopic defects in the eye’s outer protective membrane. Amoeba in water or soil can cross the membrane at a vulnerable point and enter the cornea.
Once acanthamoebae enter the eye, they feed on sugars in tears and other eye fluids. The body, aware of a foreign presence, mounts an attack against the invader, often with devastating consequences to eyesight.
The eye’s first response, Binder explained, is to fill with the cornea with white blood cells, otherwise known as pus. The cornea turns opaque, and vision deteriorates quickly. The eye’s natural defenses try to enclose the amoebae in scar tissue, but that strategy can cause glaucoma and cataracts.
Visvesvara is investigating new cases of acanthamoeba keratitis and is preparing a CDC report for the nation’s physicians. Meanwhile, he urges lens wearers to follow the ophthalmologists’ new guidelines.
